What’s Going On?

What we are doing here is setting the width of MN1 to 100nm, 200nm, 400nm, 800nm and 1.6µm. Each time we set the width of this device, we run a transient simulation. We then plot the values of gm and Vgst of MN1 for each run.

We then set the width of MN2 to 2µm, 3µm, 5µm, 10µm, 20µm and do as before.

Simulation Results

Here are the transconductance and Vgst curves of MN1. Looking first at the Vgst curve, we can see that the looking at the fist run, represented by the red line, through to the last run represented by the brown line, Vgst is above 0V all the time, so we’re in the saturation region.Only just in the case of W=1.6µm.

Looking at the transconductance curves for this device, we see that varying the width of the device changes the transconductance from ~6.5µS to ~18µS. So for a 16X increase in width, we see a 3X change in transconductance

Vgst MN1

gm MN1

Here are the transconductance and Vgst curves of MN2. Looking first at the Vgst curve, we can see that the looking at the fist run, represented by the red line, through to the last run represented by the brown line, Vgst is below 0V all the time, so we’re in the subthreshold region.

Looking at the transconductance curves for this device, we see that varying the width of the device changes the transconductance from ~22.5µS to ~24.8µS.

In this case the width of the last run is 10X that of the first, yet we see almost no change in transconductance at all.